The present invention generally relates to an electricity meter for monitoring the amount of consumed electricity. More specifically, the present invention relates to a three-phase electricity meter incorporating a test switch that allows for meter testing without accessing the meter housing.
Presently, three-phase meters are available for monitoring the amount of three-phase electricity consumed by a facility. Typically, three-phase electricity meters are provided for large residential or industrial applications. A typical three-phase electricity meter monitors the amount of electricity consumed by the facility over each of the three phases of the supplied electricity. The three-phase electricity meter includes internal circuitry that monitors the amount of electricity consumed over each of the three phases of the power supply. Many different types of measurement circuits have been developed to accurately measure the amount of electricity consumed over each of the three phases.
Since three-phase electricity meters are often used in locations that consume a large amount of power, electrical utilities have a great incentive to test the three-phase electricity meters for accuracy prior to the installation of the three-phase electricity meter in the field.
The testing of a three-phase electricity meter typically involves placing the three-phase electricity meter into a test circuit and supplying high levels of both voltage and current to the electricity meter to determine whether the electricity meter is properly measuring the amount of consumed electricity. Typically, the test circuit is designed such that the circuit can supply both high voltage over the three phases and a high amount of current. Test circuits of this type are typically very expensive, which increases the cost for the utility.
In an attempt to avoid utilizing the expensive testing circuit described above, utilities test three-phase meters by utilizing separate current and voltage sources. The circuitry required to supply separate voltage and current sources is significantly less expensive and less bulky. When utilizing separate voltage and current sources, the internal contacts within the electricity meter must be altered during the testing. Typically, this requires testing personnel to isolate the voltage input circuits from the current inputs by physically opening individual links connected to each phase on the meter. Once the testing is complete, the electricity meter is returned to its normal condition by reversing this procedure. This testing process is labor intensive and thus increases the cost to test each of the three-phase electricity meters.
Therefore, it is an object of the present invention to provide an electricity meter that can be tested utilizing separate high voltage and high current supplies. Further, it is an object of the present invention to provide a three-phase electricity meter that includes the ability to alter the internal connections simultaneously, thereby reducing the number of operations by a factor of three.
The present invention is directed to a three-phase electricity meter that is operable to measure and display the amount of consumed three-phase electricity at either a residence or industrial facility. The three-phase electricity meter is configured to be received within a conventional socket-type location such that the flow of three-phase electricity passes through the meter before being consumed at the facility. The three phase electricity meter includes a meter housing having a base member and a cover member. Preferably, the meter housing is enclosed and sealed such that the operating circuitry contained within the meter housing is protected from the environment.
The electricity meter of the present invention includes an internal circuit board that is enclosed within the housing and includes the measurement and operating circuitry required to determine the amount of three-phase electricity consumed by the facility. Typically, the measurement circuitry is mounted on one side of the circuit board, while the various contacts required to receive the supply of three-phase electricity are connected to the back side of the circuit board.
The electricity meter of the present invention includes three separate bus bars that each include a pair of connection blades that extend through the back, base plate of the meter housing. Each of the bus bars typically includes two spaced blades that are positioned in a configuration such that the electricity meter can be received within a conventional socket-type receptacle. As indicated, the blades on each of the bus bars extend through the base plate of the meter housing such that the meter housing does not need to be opened to access the blades of the bus bars.
A plurality of contact members are contained within the open interior of the meter housing, each of which provide an electrical connection between one of the bus bars and the circuit board. Preferably, each of the contact members is associated with only one of the bus bars such that each bus bar is coupled to the circuit board independently from the other remaining bus bars.
In accordance with the present invention, each of the contact members includes a first end that is in contact with the circuit board and a second end that is biased into contact with one of the bus bars. Specifically, a flexible finger is formed on each contact member from a material having a pre-stressed configuration such that the second end of the flexible finger is biased into contact with one of the bus bars. During normal operating conditions, the contact between the flexible finger of the contact member and the bus bar provides an electrical path between one of the bus bars and the circuit board contained within the electricity meter.
The electricity meter of the present invention includes a test switch member that is movable between a testing position and an operating position. When the test switch member is in the operating position, each of the contact members is in contact with one of the bus bars such that electricity can flow from the bus bars to the circuit board.
When the test switch member is moved to the testing position, the single test switch member moves each of the flexible fingers of the contact members out of contact with the respective bus bars such that the electrical interconnection between the bus bars and the circuit board is interrupted. The test switch member includes a plurality of engagement posts for engaging the flexible fingers of the contact members. Specifically, the flexible finger of each contact member is entrapped between a pair of the engagement posts. When the test switch member is moved to the testing position, the engagement post moves the flexible fingers away from and out of contact with the respective bus bars.
Each of the contact members includes a connecting pin that is accessible from the exterior of the enclosed housing for the electricity meter. The connecting pins provide a point of attachment for a supply of voltage to be fed into the electricity meter. During test conditions, the test switch member is moved to its testing position to separate the flexible finger of each contact member and the respective bus bars. Once the electrical connection is broken between the contact members and the bus bars, a test voltage can be selectively applied to each of the contact members through the respective connecting pins. At the same time, a separate test current can be applied to each of the bus bars such that separate sources for the current and voltage can be used to test the electricity meters.
In accordance with the present invention, the bus bars can be isolated from the circuit board by moving a single test switch member that is accessible from the exterior of the enclosed meter housing. Once the bus bars have been isolated, a test voltage or current can be supplied to the electricity meter from exterior to the enclosed housing. After testing is complete, the test switch member can be moved to the operating position and the electricity meter put into field service.
Various other features, objects and advantages of the invention will be made apparent from the following description taken together with the drawings.